1. Technical Field
Fluid dispensers are disclosed that comprise a piston in a piston chamber. The dispensers are particularly suitable for dispensing and metering viscous compositions such as pigment pastes, colorants, cosmetics, chemicals, paints or the like.
2. Description of the Related Art
Mixing compositions such as paint formulations requires dispensing of both large volumes of liquid as well as smaller quantities. Dispensers designed for dispensing the larger volumes have a relatively large piston diameter, which makes them suitable for dispensing large volumes, but not small volumes. Accordingly, the reproducibility and accuracy of the dispensing of small volumes using such large capacity dispensers is insufficient.
U.S. Pat. No. 4,964,534 discloses a double piston for a colorant dispenser with a small piston movable within a bore in a larger piston. The shaft of the small piston runs through the shaft of the larger piston.
A need exists for a fluid dispenser with accurate and reproducible metering when dispensing in variable volumetric ranges, which can easily and effectively cooperate with a regular operating module, e.g., of a colour mixing apparatus.